_initialize_backend doesn't need to do anything for GRBackend

src/backends.jl

@@ -316,6 +316,9 @@ function _initialize_backend(pkg::AbstractBackend)
     end
 end
 
+_initialize_backend(pkg::GRBackend) = nothing
+
+
 function add_backend_string(pkg::AbstractBackend)
     sym = backend_package_name(pkg)
     """

src/backends/gr.jl

@@ -6,6 +6,7 @@
 import GR
 export GR
 
+
 # --------------------------------------------------------------------------------------
 
 const gr_linetype = KW(